The present invention relates to an electric rotary machine using a magnet for a field, and particularly, to an electric rotary machine for a power generation system and a control method thereof.
In a conventional permanent magnet electric rotary machine, an inductive electromotive force E is determined by a constant magnetic flux "PHgr" generated by a permanent magnet arranged in a rotor and a rotating angular velocity xcfx89 of an electric rotary machine. Specifically, when the rotating angular velocity xcfx89 (rotating speed) of the electric rotary machine increases, the inductive electromotive force of the electric rotary machine rises in proportion thereto. Hence, operation in a high rotation region is difficult. Conventionally, operation in the high speed was made possible by the field weakening control technique.
But, this technique has drawbacks due to the heat generation by a field weakening current and lowered efficiency.
In a prior art method, a mechanism making use of a centrifugal force using a spring and a governor, as a field weakening method of magnetic flux generated by a permanent magnet is utilized.
Also, the construction of a spring and a governor is complex and costly.
The present invention provides an electric rotary machine which allows ease of fabrication and enables a field weakening of magnetic flux generated by a permanent magnet. Further, the present invention provides a power generation system provided with a permanent magnet type electric rotary machine capable of obtaining high torque characteristics in a low rotation region, such as start of a heat engine, and high output power generation characteristics in a high rotation region.
In an object of the present invention an electric rotary machine including a rotor having a field magnet provided on a shaft is provided the field magnet comprising a first field magnet with magnetic poles of sequentially different polarities arranged in a rotational direction, a second field magnet with magnetic poles of sequentially different polarities arranged in a rotational direction and the second field magnet is rotatable on the shaft and displaced axially with respect to the first field magnet.
In another object of the present invention an electric rotary machine including a rotor having a field magnet provided on a shaft is provided the field magnet comprising a first field magnet with magnetic poles of sequentially different polarities arranged in a rotational direction, a second field magnet with magnetic poles of sequentially different polarities arranged in a rotational direction wherein the second field magnet is rotatable on the shaft and displaced axially with respect to the first field magnet and a composite magnetic field created by the field magnets is changed.
In yet another object of the present invention a power generation system and a turbine power generation system is provided utilizing the electric rotary machine of the present invention. Further, a method of controlling a field magnet in a electric rotary machine is provided.